#include <iostream>
using namespace std;


int main(void)
{
	int commit(int k, int n);
	int n, k;
	cin >> n >> k;
	cout << commit(n, k) << endl;
}


int commit( int n,int k)
{
	if (k > n)return 0;
	else if(k == 0 || n == k) return 1;
	else return commit(n - 1, k) + commit(n - 1, k - 1);
}



